Margins for geometric uncertainty around organs at risk in radiotherapy
Margins for geometric uncertainty around organs at risk in radiotherapy
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DOI：
10.1016/s0167-8140(02)00015-4
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发表时间：
2002-03-01
影响因子：
5.7
通讯作者：
Mijnheer, B
中科院分区：
文献类型：
--
作者：
McKenzie, A;van Herk, M;Mijnheer, B
背景和目的：ICRU报告62建议在危险器官（ORs）周围绘制边缘以产生计划危险器官体积（PRVs），以解释放射治疗过程中的几何不确定性。本文提出了一种绘制这种切缘的算法，并将推荐的切缘宽度与临床实践中的例子进行了比较，并讨论了该方法的局限性。方法：使用这样定义的PRV，尽管存在几何上的不确定性，但治疗计划系统在PRV内计算的剂量可以在一定的置信水平上代表手术室中的剂量。一个合适的水平是，在大多数情况下（90%），PRV的剂量-体积直方图不会低于OR中的高剂量成分。为了在临床实践中为如何做到这一点提供指导，本文根据相对于处方剂量的耐受剂量区分了手术室的类型，并建议了串联结构和平行结构手术室的适当界限。结果：在一些大型平行手术中，临床医生可能认为省略切缘的并发症风险是可以接受的。否则，对于所有类型的OR，系统的，处理制备的不确定性可以通过OR -> PRV边缘宽度为1.3Sigma来调节。这里，Sigma是综合系统（治疗准备）不确定度的标准差。在串行手术室或小型并行手术室的情况下，应考虑到日常治疗执行错误（设置和器官运动）引起的模糊影响。在高剂量区域附近，模糊会使等剂量偏离治疗计划系统显示的未模糊边缘，偏移量可以用0.5西格玛表示。根据耐受剂量相对于详细计划剂量分布的大小，这个余量可用于增加或减少已经为系统不确定性计算的余量。如果在描述OR之前不知道详细的分布，那么串行或小并行OR的总余量应为1.3Sigma + 0.5sigma。给出了应用该算法产生与临床使用的相似的ORs周围边缘宽度的例子。结论：PRVs适用于正向规划和逆向规划。串行和并行结构的口服脊灰病毒的剂量-体积直方图需要仔细解释。然而，使用所提出的算法在串联和平行手术室周围绘制边界，可以提醒剂量学家/放射肿瘤学家在个别治疗计划中可能出现高闭合并发症，如果没有绘制这样的边界，可能会错过这些并发症。(C) 2002爱思唯尔科学爱尔兰有限公司版权所有。
Background and purpose: ICRU Report 62 Suggests drawing margins around organs at risk (ORs) to produce planning organ at risk volumes (PRVs) to account for geometric uncertainty in the radiotherapy treatment process. This paper proposes an algorithm for drawing such margins, and compares the recommended margin widths With examples from clinical practice and discusses the limitations of the approach.Method: The use of the PRV defined in this way is that, despite the geometric uncertainties, the dose calculated within the PRV by the treatment planning system can be used to represent the dose in the OR with a certain confidence level. A suitable level is where, in the majority of cases (90%), the dose-volume histogram of the PRV will not under-represent the high-dose components in the OR. In order to provide guidelines on how to do this in clinical practice, this paper distinguishes types of OR in terms of the tolerance doses relative to the prescription dose and suggests appropriate margins for serial-structure and parallel-structure ORs.Results: In some instances of large and parallel ORs, the clinician may judge that the complication risk in omitting a margin is acceptable. Otherwise, for all types of OR, systematic, treatment preparation uncertainties may be accommodated by an OR --> PRV margin width of 1.3Sigma. Here, Sigma is the standard deviation of the combined systematic (treatment preparation) uncertainties. In the case of serial ORs or small, parallel ORs, the effects of blurring caused by daily treatment execution errors (set-up and organ motion) should be taken into account. Near a region of high dose, blurring tends to shift the isodoses away from the unblurred edge as shown on the treatment planning system by an amount that may be represented by 0.5sigma. This margin may be used either to increase or to decrease the margin already calculated for systematic uncertainties, depending upon the size of the tolerance dose relative to the detailed planned dose distribution. Where the detailed distribution is unknown before the OR is delineated, then the overall margin for serial or small parallel ORs should be 1.3Sigma + 0.5sigma. Examples are given where the application of this algorithm leads to margin widths around ORs similar to those in use clinically.Conclusions: Using PRVs is appropriate both for forward and inverse planning. Dose-volume histograms of PRVs for serial- and parallel-structure ORs require careful interpretation. Nevertheless, use of the proposed algorithms for drawing margins around both serial and parallel ORs can alert the dosimetrist/radiation oncologist to the possibility of high-close complications in individual treatment plans, which might be missed if no such margins were drawn. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.